Future optical fiber telecommunication networks will require new types of semiconductor lasers. High speed single frequency lasers are needed for toll lines and local networks

while wavelength tunable lasers will be used for local oscillators in heterodyne receivers and wavelength switching in packet switches. This paper presents a brief review of the present status of these new semicondu■tor laser sources in the 1.3～1.55μm longwavelength region

with applications in the future broadband optical fiber transmission systems.